Abstract

Recently, controversy in the care of severely-profoundly deaf children has centred on whether they should be provided with bilateral cochlear implants (two implants, one in each ear) rather than a unilateral cochlear implant (one implant in one ear). Potentially, implanting both ears rather than one could improve children’s spatial listening skills, meaning the ability to localise sources of sound (by comparing the intensity and timing of sounds arriving at the two ears) and to perceive speech in noise (by attending to whichever ear gives the better signal-to-noise ratio). The overall aim of the studies reported in this thesis was to assess whether bilateral implantation for children is more effective than unilateral implantation in improving spatial listening skills and quality of life. The first study measured the relationship between spatial listening skills and age in normally-hearing children. The second study compared the spatial listening skills of unilaterally- and bilaterally-implanted children. Whilst controlling for confounds, the bilateral group performed significantly better than the unilateral group on tests of sound-source localisation. Moreover, the bilateral group, but not the unilateral group, displayed improved speech perception when the source of a masking noise was moved from the front to either side of the head. Neither group of implanted children performed as well as normally-hearing children on tests of the ability to localise sources of sound and to perceive speech in noise. The third study measured the spatial listening skills of normally-hearing adults when listening to simulations of unilateral or bilateral implants. The differences in performance between simulations were similar to the differences in performance between groups of implanted children, which provides further evidence that the children's performance was primarily influenced by the number of implants they used rather than by confounds. The fourth study found that there was no significant difference between bilaterally- and unilaterally-implanted children in parental estimates of quality of life. The fifth study presented informants, who were not the parents of hearing-impaired children, with descriptions of a hypothetical child with unilateral or bilateral implants. The informants judged that the bilaterally-implanted child had a higher quality of life than the unilaterally-implanted child. These studies indicate that bilateral implantation for children is more effective than unilateral implantation in enabling spatial listening skills, but the extent of any gain in quality of life remains uncertain.